This invention relates to a bat, and more particularly to a bat with inner and outer tubular members with lubricating material therebetween, and a method for manufacturing such.
Tubular metallic softball and baseball bats are well known in the art. A familiar example is a tubular aluminum bat. Such bats have the advantage of a generally good impact response, meaning that the bat effectively transfers power to a batted ball. This effective power transfer results in ball players achieving good distances with batted balls. An additional advantage is improved durability over crack-prone wooden bats.
Even though present aluminum bats perform well, there is an ever-continuing quest for bats with better hitting capability. Accordingly, one important need is to optimize the impact response of a bat. Generally speaking, impact response is best when a bat undergoes the greatest elastic deflection, before rebounding with the greatest force in the longest amount of time. Optimization of these factors increases the xe2x80x9cspringxe2x80x9d of a ball off a bat, yielding a bat with superior power transfer and facility for xe2x80x9cslugging.xe2x80x9d
Further constraining the design of aluminum bats is the requirement that the elastic deflection not be accompanied by any plastic deformation. Plastic deflection lessens the power transferred to a ball and leaves the bat permanently dented. Thus, aluminum bat design is driven by the elastic and plastic deformation characteristics of aluminum. For example, when the tubular wall is too thin, a desirable large amount of elastic deflection is achieved, but with unwanted permanent plastic deformation. On the other hand, when the aluminum tubular wall is too thick, the bat may be too stiff to elastically deflect appreciably. In this case, the bat responds with relatively little spring, resulting in lower power transfer.
The prior art includes tubular bats using inserts. Most often inserts are used for vibration deadening purposes. U.S. Pat. No. 3,963,239 to Fujii discloses a metallic bat frame with a large-diameter impact portion receiving an insert to adjust the weight and improve the xe2x80x9crepelling actionxe2x80x9d of the bat. Fujii teaches an insert in tight abutment within the tubular frame, so that the insert is fixed relative to the frame. The engagement is improved by forcing the insert into the tapered intermediate portion of the bat and/or by gluing the insert within the frame. The tightly fitted Fujii insert simply acts to thicken the wall of the impact portion of the bat.
In light of the shortcomings of the prior art, it is an object of the present invention to provide an improved bat.
It is another object of the invention to provide a simple construction for a tubular bat with inner and outer tubular members.
In accordance with an embodiment of the present invention, a bat having an elongate impact portion is formed with a first tubular member, and a second tubular member substantially concentric with the first tubular member. The first and second tubular members have close fitting facing cylindrical surfaces throughout a majority of the length of the impact portion and lubricating material is interposed between the facing cylindrical surfaces.
Further, in accordance with an embodiment of the present invention, an elongate tubular metal member has a circular striking portion, with the striking portion having an interior surface defining an interior cavity. An elongate tubular metal insert is located within the interior cavity and has an exterior surface complementary to, and throughout a majority of its length fitting against, the interior surface of the striking portion. Lubricating material is interposed between the interior surface and the exterior surface to permit relative movement between the insert and the surrounding tubular member when a ball is batted.
Another object of the present invention is to provide a method for producing an improved bat.